The relatively new field of quantum metrology concerns the utilisation of nonclassical phenomena to improve measurements and estimations. For example, by deploying squeezed optical states or entangled particles, classical statistical bounds on parameter estimation can be surpassed. Notably, the use of N00N-entangled probe particles in estimation strategies can give significant improvements to estimators’ errors. Given the fundamental nature of measurements and estimation in science, the uses of quantum metrology are vast. In the coming 5 – 10 years, quantum metrology will become integrated in technologies for the most precise measurements of electric/magnetic fields, nanometre measurements of distances, fast benchmarking of quantum computers, the detection of gravitational waves, etc.

The Cavendish QI group has recently expanded its work on quantum metrology. From a theory perspective, the group has collaborated with the quantum-information groups at Harvard and MIT, where quantum metrology was first realised. The collaboration has resulted in a thorough demonstration of quantum advantages available in post-selected parameter estimation. Whilst previous theory results have aimed at maximising the Fisher information per input state, the QI group’s protocols provide a quantum advantage in achieving non-classically high values of Fisher information per real experimental “cost” (temporal or otherwise). The group is currently collaborating with the University of Toronto to experimentally realise these results. The group also has an ongoing metrology collaboration with Hitachi Ltd.